1. Technical Field
The present invention relates to a liquid droplet discharging head and a liquid droplet discharging apparatus.
2. Related Art
As a component of a liquid droplet discharging apparatus such as an ink-jet printer, a liquid droplet discharging head that includes a piezoelectric element for ejecting liquid such as ink in the form of droplets is known. For example, the piezoelectric element stretches and shrinks to deform a diaphragm plate when a driving signal is supplied thereto. This causes a pressure change in a pressure chamber that is formed under the piezoelectric element. As a result, the liquid supplied to the pressure chamber is discharged as droplets through a nozzle hole. To protect the piezoelectric substance layer of a piezoelectric element, which is susceptible to damage due to effects of ambient conditions such as, for example, moisture in the air, an upper electrode covers the piezoelectric substance layer in a structure of related art. An example of such a structure is disclosed in JP-A-2005-88441.
An elastic film 50 and an insulator film 55 that make up a diaphragm plate are shown in FIG. 3 of JP-A-2005-88441. In the illustrated structure, the thickness of the insulator film 55 tends to be reduced because it is subjected to over-etching in the processes of the patterning of a lower electrode, the piezoelectric substance, and the upper electrode. Therefore, there is a possibility that the diaphragm plate cracks when the piezoelectric element is driven for a long time.